In certain types of surgical procedures, the use of surgical staples has become the preferred method of joining tissue and, as such, specially configured surgical staplers have been developed for these applications. For example, intra-luminal or circular staplers have been developed for use in a surgical procedure known as an anastomosis. Circular staplers useful for performing an anastomosis are disclosed, for example, in U.S. Pat. Nos. 5,104,025; 5,205,459; 5,285,945; and 5,309,927 which are each herein incorporated by reference in their respective entireties.
One form of an anastomosis comprises a surgical procedure wherein sections of intestine are joined together after a diseased portion has been excised. The procedure requires re-joining the ends of the two tubular sections together to form a continuous tubular pathway. Previously, this surgical procedure was a laborious and time consuming operation. The surgeon had to precisely cut and align the ends of the intestine and maintain the alignment while joining the ends with numerous suture stitches. The development of circular staplers has greatly simplified the anastomosis procedure and also decreased the time required to perform an anastomosis.
In general, a conventional circular stapler typically consists of an elongated shaft that has a proximal actuating mechanism and a distal stapling mechanism mounted to the shaft. The distal stapling mechanism commonly consists of a fixed stapling cartridge that contains a plurality of staples configured in a concentric circular array. A round cutting knife is concentrically mounted in the cartridge interior to the staples for axial travel therein. Extending axially from the center of the cartridge is a movable trocar shaft that is adapted to have a staple anvil removably coupled thereto. The anvil is configured to form the ends of the staples as they are driven into it. The distance between a distal face of the staple cartridge and the staple anvil is controlled by an adjustment mechanism mounted to the proximal end of the stapler shaft for controlling the axial movement of the trocar. Tissue clamped between the staple cartridge and the staple anvil is simultaneously stapled and cut when the actuating mechanism is activated by the surgeon.
When performing an anastomosis using a circular stapler, the intestine is typically stapled using a conventional surgical stapler with double rows of staples being emplaced on either side of the diseased portion of intestine to be removed. The target section is simultaneously cut as the adjoining end is stapled. After removing the diseased portion, the surgeon typically inserts the anvil into the proximal end of the lumen, proximal of the staple line. This is done by inserting the anvil head into an entry port cut into the proximal lumen by the surgeon. On occasion, the anvil can be placed transanally, by placing the anvil head on the distal end of the stapler and inserting the instrument through the rectum. The surgeon then ties the proximal end of the intestine to the anvil shaft using a suture or other conventional tying device. Next, the surgeon cuts excess tissue adjacent to the tie and the surgeon attaches the anvil to the trocar shaft of the stapler. The surgeon then closes the gap between the anvil and cartridge, thereby clamping the proximal and distal ends of the intestine in the gap. The surgeon next actuates the stapler causing several rows of staples to be driven through both ends of the intestine and formed, thereby joining the ends and forming a tubular pathway. Simultaneously, as the staples are driven and formed, the concentric circular knife blade is driven through the intestinal tissue ends, cutting the ends adjacent to the inner row of staples. The surgeon then withdraws the stapler from the intestine and the anastomosis is complete.
During the above-described surgical procedures, the clinician generally strives to obtain a tight enough staple line to prevent leakage and bleeding and to achieve “tissue-to-tissue” contact which promotes tissue healing. In general, by controlling the amount of compression that is applied to the tissue, better stapling and healing results will be achieved. Achieving a desired amount of tissue compression becomes challenging when dealing with thick tissues and thin tissues. For example, when stapling thinner tissue, it is necessary to move to the lower end of the compression range to obtain compression of the tissue—without over compressing it. When stapling thicker tissues, the proper compression will be achieved at a larger gap setting.
A simple robust means to measure this compression would be to use a compliant member and an indicator to measure displacement similar to a spring force scale. Such arrangements, however, must be able to withstand the forces required to form the staples and to cut through a break away washer which is commonly mounted in the anvil. In some instances, for example, such forces may exceed 300 lbf and must be restrained without deflection to ensure the proper formed staple height is achieved. Such devices, however, present additional challenges to the user. In particular, once the anvil has been properly positioned, it is necessary that the anvil not move during firing. Those anvil systems that are compliant in nature may facilitate undesirable movement or deflection of the anvil during firing which could adversely affect proper staple formation.
Thus, the need exists for an anvil locking system that can be used to selectively retain the anvil in a desired position during stapling.
The foregoing discussion is intended only to illustrate some of the shortcomings present in the field of the invention at the time, and should not be taken as a disavowal of claim scope.